Clinical Profile of Patients on Antiepileptic Drugs Experiencing Ataxia as an Adverse Drug Reaction: A Longitudinal Observational Study

Introduction: Ataxia is one the common adverse drug effect caused by Antiepileptic Drugs (AEDs). It can result from either single therapeutic dose of a particular drug, prolonged use of same drug or acute poisoning.

Aim: To determine the disease burden and clinical profile of patients who are on AEDs and develop ataxia.

Materials and Methods: This was a longitudinal observational study, carried out at Mahatma Gandhi Medical College and Research Institute, Puducherry, from January 2016 to March 2022. The clinical characteristics of patients who presented with ataxia on AEDs and with no previous history of ataxia were documented. Based on the time of onset of ataxia patients were divided into three groups: Group A- Ataxia developed within 24 hours of onset of drug intake; Group B- Ataxia developed within 24 to 72 hours from prescription of drug; Group C- Ataxia developed after 72 hours from the time of drug administration. Patients were further classified into those having sensory ataxia and cerebellar ataxia. Based on the time of clinical resolution patients were classified into three subgroups: Group 1- Clinical resolution within 72 hours; Group 2- Clinical resolution in 72 to 144 hours; and Group 3- Clinical resolution after 144 hours. Data was collected systematically and results were statistically analysed using Microsoft Excel spreadsheet software program.

Results: Out of the total number of epileptic patients (1600) on AEDs, 34 patients developed ataxia. Of these 34 patients, 15 (44.11%) were on Phenytoin, 12 (35.29%) were on Carbamazepine, 3 (8.82%) were on Gabapentin, 2 (5.88%) were on Zonisamide, and 2 (5.88%) were on Lamotrigine. Dose of these drugs were modified within one day, after one and three weeks and after one month in 9 (26.47%), 7 (20.58%), 12 (35.29%), and 4 (11.76%) patients, respectively. Two patients had presented with acute poisoning. Half, 50% (n=17) patients had symptoms of sensory ataxia and remaining half had symptoms of cerebellar ataxia.

Conclusion: Ataxia secondary to AEDs is seen with both the older and newer drugs. Awareness of the possibility of AEDs induced ataxia can help in early diagnosis and its management.